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SUMMARY:Philipp Höhn (OIST\, University College London)
DTSTART;VALUE=DATE-TIME:20201007T150000Z
DTEND;VALUE=DATE-TIME:20201007T160000Z
DTSTAMP;VALUE=DATE-TIME:20210419T100140Z
UID:QG-AA/1
DESCRIPTION:Title: Pr
oblem of time\, relational observables and quantum covariance\nby Phil
ipp Höhn (OIST\, University College London) as part of Quantum Gravity Ac
ross Approaches\n\n\nAbstract\nThe diffeomorphism symmetry of general rela
tivity leads to the infamous problem of time\, haunting especially canonic
al approaches to quantum gravity. The core question it raises is how to de
fine quantum dynamics in a diffeomorphism-invariant context (in the absenc
e of external references such as boundaries) and is intimately tied with t
he more general question of what are observables in a background-independe
nt quantum theory. Relational observables are one way of addressing these
challenges. The underlying idea is to localize physical quantities of inte
rest relative to other dynamical degrees of freedom\, chosen as a dynamica
l reference system\, rather than a spacetime background. A comprehensive r
elational picture then warrants covariance to be extended to changes of dy
namical reference system. In this talk\, I will offer an overview over ach
ievements and challenges of the relational approach\, as well as perspecti
ves on quantum gravity arising therefrom.\n
LOCATION:https://researchseminars.org/talk/QG-AA/1/
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BEGIN:VEVENT
SUMMARY:William Donnelly (Perimeter Institute)
DTSTART;VALUE=DATE-TIME:20201102T170000Z
DTEND;VALUE=DATE-TIME:20201102T180000Z
DTSTAMP;VALUE=DATE-TIME:20210419T100140Z
UID:QG-AA/2
DESCRIPTION:Title: Dr
essed observables in perturbative quantum gravity\nby William Donnelly
(Perimeter Institute) as part of Quantum Gravity Across Approaches\n\nAbs
tract: TBA\n
LOCATION:https://researchseminars.org/talk/QG-AA/2/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Daniel Harlow (MIT)
DTSTART;VALUE=DATE-TIME:20201202T170000Z
DTEND;VALUE=DATE-TIME:20201202T183000Z
DTSTAMP;VALUE=DATE-TIME:20210419T100140Z
UID:QG-AA/3
DESCRIPTION:Title: Gl
obal symmetry\, Euclidean gravity\, and the black hole information problem
\nby Daniel Harlow (MIT) as part of Quantum Gravity Across Approaches\
n\n\nAbstract\nIn this talk I will show how the essential ingredients of r
ecent calculations of the Page curve of an evaporating black hole can be u
sed to generalize a recent argument against global symmetries beyond the A
dS/CFT correspondence to more realistic theories of quantum gravity\, illu
strating a close connection between the absence of global symmetries and a
unitary resolution of the black hole information problem. I'll also give
several low-dimensional examples of quantum gravity theories which do not
have a unitary resolution of the black hole information problem\, and whic
h therefore can and do have global symmetries. Motivated by this discussio
n\, I'll conjecture that in a certain sense Euclidean quantum gravity is e
quivalent to holography. Based on recent work with Edgar Shaghoulian.\n
LOCATION:https://researchseminars.org/talk/QG-AA/3/
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BEGIN:VEVENT
SUMMARY:Kasia Rejzner
DTSTART;VALUE=DATE-TIME:20210118T170000Z
DTEND;VALUE=DATE-TIME:20210118T183000Z
DTSTAMP;VALUE=DATE-TIME:20210419T100140Z
UID:QG-AA/4
DESCRIPTION:Title: No
n-local observables in quantum gravity from the algebraic QFT perspective<
/a>\nby Kasia Rejzner as part of Quantum Gravity Across Approaches\n\nAbst
ract: TBA\n
LOCATION:https://researchseminars.org/talk/QG-AA/4/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Renate Loll
DTSTART;VALUE=DATE-TIME:20210217T170000Z
DTEND;VALUE=DATE-TIME:20210217T183000Z
DTSTAMP;VALUE=DATE-TIME:20210419T100140Z
UID:QG-AA/5
DESCRIPTION:Title: Ob
servables for Quantum Gravity: Going Nonperturbative\nby Renate Loll a
s part of Quantum Gravity Across Approaches\n\n\nAbstract\nThe physical na
ture and explicit construction of observables in quantum gravity depend on
length scale and context\, and tend to be very different in perturbative
and nonperturbative regimes. My talk will focus on the latter\, which is c
haracterised by the absence of a pre-existing background and where spaceti
me is not described by a smooth metric tensor. What constitutes appropriat
e (pre-)gravitational observables near the Planck scale is not known a pri
ori\, and their operational definition depends on how diffeomorphism symme
try is implemented nonperturbatively. Natural candidates are "quantum gene
ralisations" of nonlocal classical observables\, which in general will nee
d to be renormalized and may display unexpected\, anomalous behaviour. To
compare with classical results\, one also needs some control on how to coa
rse-grain. The construction and implementation of nonperturbative quantum
observables poses creative and technical challenges that can be addressed
successfully in sufficiently complete candidate theories\, as I will illus
trate in the context of Causal Dynamical Triangulations.\n
LOCATION:https://researchseminars.org/talk/QG-AA/5/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Philipp Hohn\, William Donnelly\, Daniel Harlow\, Kasia Rejzner\,
Renate Loll
DTSTART;VALUE=DATE-TIME:20210408T130000Z
DTEND;VALUE=DATE-TIME:20210408T143000Z
DTSTAMP;VALUE=DATE-TIME:20210419T100140Z
UID:QG-AA/6
DESCRIPTION:Title: Ob
servables in Quantum Gravity: Panel Discussion\nby Philipp Hohn\, Will
iam Donnelly\, Daniel Harlow\, Kasia Rejzner\, Renate Loll as part of Quan
tum Gravity Across Approaches\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/QG-AA/6/
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